Authentication bypass via untrusted JWT algorithm selection
Published Jan 13, 2026 · Updated Jan 13, 2026
JWT algorithm confusion in Hono before 4.11.4 allows remote attackers to forge tokens accepted by applications using JWK/JWKS authentication. When a selected JWK omits alg, the middleware's verifyWithJwks path trusts the unverified JWT header's alg value to choose signature verification. Exposure requires JWK/JWKS middleware without an explicit asymmetric-algorithm allowlist; accepted tokens can carry attacker-controlled claims and bypass authentication or authorization.
Summary
What happened
JWT algorithm confusion in Hono before 4.11.4 allows remote attackers to forge tokens accepted by applications using JWK/JWKS authentication. When a selected JWK omits alg, the middleware's verifyWithJwks path trusts the unverified JWT header's alg value to choose signature verification. Exposure requires JWK/JWKS middleware without an explicit asymmetric-algorithm allowlist; accepted tokens can carry attacker-controlled claims and bypass authentication or authorization.
The record
- CVE
- CVE-2026-22818
- Published
- Jan 13, 2026
- Updated
- Jan 13, 2026
- Vendor
- Hono
- Product
- Hono
- Classifications
- CWE-347, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jan 13, 2026CVE publishedPublication date reported by the CVE source.
- Jan 13, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=< 4.11.4
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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